The present invention relates to a surveying instrument for sighting a measuring point by horizontally rotating a frame and vertically rotating a telescope by motors and for performing a distance measurement and an angle measurement.
A surveying instrument, for instance, a total station, has a telescope unit for sighting a measuring point. The telescope unit is rotatably supported by a frame unit in a vertical direction, and the frame unit is rotatably supported by a base unit in a horizontal direction. Further, the total station has a motor for rotating the telescope unit and a motor for rotating the frame unit.
As a conventionally used motor, an ultrasonic motor and a stepping motor are used, for instance. In these motors, in a case where an output shaft of the motor and a rotation shaft are connected to each other, an eccentricity is occurred between the output shaft and the rotation shaft due to a dimensional error, a mounting error and the like. Therefore, it is necessary to provide a mechanism for absorbing the eccentricity.
Conventionally, a coupling is provided at a connecting portion between the output shaft of the motor and the rotation shaft, for instance, and the eccentricty between the output shaft of the motor and the rotation shaft is absorbed by the coupling. However, by providing the coupling, the motor and its peripheral part become bulky, and a space in a frame is narrowed, which prevented a provision of other components.
It is to be noted that Japanese Patent Publication Laid-open. No. H11-311517 discloses a surveying instrument in which an arm of the ultrasonic motor extending from a motor case is fixed to an extension rod extending from a columnar portion via a universal joint and an eccentricity between the motor case and the columnar portion caused by the dimensional error or the mounting error is absorbed by the universal joint.